During growth, aerobic organisms require oxygen and produce carbon dioxide in order to grow and maintain a pure strain of a selected organism in a cultivation system, it is advantageous to exclude competing organisms. This can include the exclusion of microorganisms from the growth environment of the cultivation system, at least until the desired organism is inoculated into the system and has sufficiently established itself. Additionally, it is important to maintain the proper oxygen to carbon dioxide ratio. Sterilizable cultivation containers are used extensively for the cultivation of edible mushrooms to provide proper growth condition, free from contaminating organisms, and to allow the exchange of oxygen and carbon dioxide with the ambient environment.
Much of this cultivation is accomplished using plastic pouches or bags. Further, the cost of bags and pouches can represent a high percentage of the total cost of raw materials for the cultivation process. This encourages the recycling of the bags and pouches. Historically, in order to provide proper venting when using recycled cultivation containers, growers often resort to cotton vent plugs. Such make-shift measures can be inherently less reliable or controllable than desired, and may not prevent the intrusion of unwanted microorganisms into a cultivation container.
Control of the internal growth environment inside a cultivation container is important, and the field has been motivated to address this issue. For example, U.S. Pat. No. 5,230,430, noting that it is desirable to maintain moisture content, attempts to provide a method for moisture control. However, the '430 patent does not teach a means for modifying the moisture conditions once the container is in use in the field to increase moisture loss. Also, the manufacture of the container of the '430 patent is complicated in that it requires the integration of a filter element into an otherwise ordinary plastic bag during the course of manufacture of the bag. Also, because of the integrated filter element of the '430 bag and similar cultivation containers, the ability to recycle containers is reduced.
Also useful for facilitating the recycling of cultivation bags are filter devices which themselves are removable and separately replaceable or recyclable. An example of a recyclable filter device is the filter cover of Stoller et al., U.S. Pat. No. 4,027,427. Stoller discloses a temporary filter cover which is installed on the neck of a plastic cultivation bag during a growth process, and is removed for reuse when the growth process is complete. Although it may be generally useful for its intended purpose, the Stoller filter cover potentially can separate from the cultivation bag when its cap is removed from its collar.
Therefore, it would be useful in the field to have an alternative reusable filter assembly having a cap that may be removed without risk of the rest of the device separating from the bag on which it is installed.